Baseband wireless network for isochronous communication

ABSTRACT

A wireless communication network system apparatus which provides for isochronous data transfer between node devices of the network, which provides at least one master node device which manages the data transmission between the other node devices of the network, which avoids or reduces interference from other wireless products and which resolves random errors associated with wireless technology including multipath fading. The system provides a communication protocol which shares the wireless transport medium between the node devices of the network, and which provides each node device on the network a designated transmit time slot for data communication.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention pertains generally to network systems forexchanging data across a shared medium. More particularly, the inventionis a wireless communication network system for isochronous data transferbetween node devices of the network system that provides at least onemaster node device which manages the data transmission between slavenode devices of the network system, and which further provides a timedivision multiple access frame definition which provides each nodedevice on the network system a transmit time slot for communication.

[0003] 2. The Prior Art

[0004] Network systems for data communication exchange have beenevolving for the past several decades. Particularly, computer networksystems have been developed to exchange information and provide resourcesharing. Network systems generally comprise one or more node deviceswhich are interconnected and capable of communicating. The most commonnetwork systems today are “wired” local area networks (LANs) and widearea networks (WANs). Normally, node devices participating in such wirednetworks are physically connected to each other by a variety oftransmission medium cabling schemes including twisted pair, coaxialcable, fiber optics and telephone systems including time divisionswitches (T-1, T-3), integrated services digital network (ISDN), andasymmetric digital subscriber line (ADSL). While wired solutions provideadequate bandwidth or data throughput between node devices on thenetwork, users participating in such networks are generally restrictedfrom mobility. Typically, users participating in a wired network arephysically limited to a specific proximity by the length of the cableattached to the user's node device.

[0005] Many common network protocols in use today are asynchronous andpacket based. One of the most popular is Ethernet or IEEE 802.3. Thesetypes of networks are optimized for bursts of packetized informationwith dynamic bandwidth requirements settled on-demand. This type ofnetwork works well for many data intensive applications in computernetworks but is not ideal for situations requiring consistent deliveryof time-critical data such as media streams.

[0006] Media streams typically require connection oriented real-timetraffic. Most media stream applications need to establish a requiredlevel of service. Dedicated connections are required with a predictablethroughput. Low traffic jitter is often a necessity and can be providedwith the use of a common network clocking reference.

[0007] Firewire, or IEEE 1394, is an emerging wireline networktechnology that is essentially asynchronous, but provides forisochronous transfers or “sub-actions”. Isochronous data is givenpriority, but consistent time intervals of data transfer is limited bymixing isochronous and purely asynchronous transfers.

[0008] Universal Serial Bus (USB) is a popular standard for computerperipheral connections. USB supports isochronous data transfer between acomputer and peripheral devices. The computer serves as bus master andkeeps the common clock reference. All transfers on USB must eitheroriginate or terminate at the bus master, so direct transfers betweentwo peripheral devices is not supported.

[0009] Wireless transmission provides mobile users the ability toconnect to other network devices without requiring a physical link orwire. Wireless transmission technology provides data communicationthrough the propagation of electromagnetic waves through free space.Various frequency segments of the electromagnetic spectrum are used forsuch transmission including the radio spectrum, the microwave spectrum,the infrared spectrum and the visible light spectrum. Unlike wiredtransmission, which is guided and contained within the physical mediumof a cable or line, wireless transmission is unguided, and propagatesfreely though air. Thus the transport medium air in wirelesscommunication is always shared between various other wireless users. Aswireless products become more pervasive, the availability of airspacefor data communication becomes proportionally more limited.

[0010] Radio waves travel long distances and penetrate solid objects andare thus useful for indoor and outdoor communication. Because radiowaves travel long distances, radio interference between multiple devicesis a common problem, thus multiple access protocols are required amongradio devices communicating using a single channel. Another commonproblem associated with wireless transmission is multi-path fading.Multipath fading is caused by divergence of signals in space. Some wavesmay be refracted off low-lying atmospheric layers or reflected offobjects such as buildings and mountains, or indoors off objects such aswalls and furniture and may take slightly longer to arrive than directwaves. The delayed waves may arrive out of phase with the direct wavesand thus strongly attenuate or cancel the signal. As a result ofmultipath fading, operators have resorted to keeping a percentage oftheir channels idle as spares when multipath fading wipes out somefrequency band temporarily.

[0011] Infrared communication is widely used for short-rangecommunication. The remote controls used on televisions, VCRs, andstereos all use infrared communication. The major disadvantage toinfrared waves is that they do not pass through solid objects, thuslimiting communication between devices to “line of sight”. Thesedrawbacks associated with the current implementation of wirelesstechnology in network systems have resulted in mediocre performance andperiodic disruption of operations.

[0012] In addition to the above noted drawbacks of Firewire and USB,there are currently no standards for wireless implementations of either.Of the wireless networks in use today, many are based at least in parton the IEEE 802.11 (wireless ethernet) extension to IEEE 802.3. Likewireless ethernet, this system is random access, using a carrier sensemultiple access with collision detect (CSMA-CD) scheme for allowingmultiple transmitters to use the same channel. This implementationsuffers from the same drawback of wireline ethernet described above.

[0013] A similar implementation intended for industrial use is that ofHyperlan™. While still an asynchronous protocol, Hyperlan™ uses priorityinformation to give streaming media packets higher access to the randomaccess channel. This implementation reduces, but does not eliminate theproblems of sending streaming media across asynchronous networks.

[0014] The Home-RF consortium is currently working on a proposal for awireless network specification suitable for home networks. The currentproposal specifies three types of wireless nodes, the connection points(CP), isochronous devices (I-nodes), and asynchronous devices (A-nodes).Isochronous transfers on the Home-RF network are intended for 64-kbpsvoice (PSTN) services and are only allowed between I-node devices andthe CP device that is connected to the PSTN network. There is noallowance in the Home-RF specification for alternative methods ofisochronous communication such as might be required for high qualityaudio or video.

[0015] The Bluetooth Special Interest Group™ has developed a standardfor a short range low bit-rate wireless network. This network standarddoes overcome some of the shortcomings of random access networks, butstill lacks some of the flexibility needed for broadband mediadistribution. The Bluetooth network uses a master device which keeps acommon clock for the network. Each of the slave devices synchronizestheir local clock to that of the master, keeping the local clock within+/−10 microseconds (μsecs). Data transfer is performed in a TimeDivision Multiple Access (TDMA) format controlled by the master device.Two types of data links are supported: Synchronous Connection Oriented(SCO) and Asynchronous Connection-Less (ACL). The Master can establish asymmetric SCO link with a slave by assigning slots to that linkrepeating with some period Tsco. ACL links between the master and slavedevices are made available by the Master addressing slave devices inturn and allowing them to respond in the next immediate slot or slots.Broadcast messages are also allowed originating only at the master withno direct response allowed from the slave devices.

[0016] Several limitations exist in the Bluetooth scheme. Allcommunication links are established between the master device and theslave devices. There are no allowances for slave-slave communicationusing either point-to-point or broadcast mechanisms. Additionally,isochronous communications are only allowed using symmetricpoint-to-point links between the master device and one slave device. TheTDMA structure used by Bluetooth is also limiting in that slot lengthsare set at N*625 μsecs where N is an integer 0

1

5.

[0017] All of the above wireless network schemes use some form ofcontinuous wave (CW) communications, typically frequency hopping spreadspectrum. The drawbacks of these systems are that they suffer frommultipath fading and use expensive components such as high-Q filters,precise local high-frequency oscillators, and power amplifiers.

[0018] Win et. al. have proposed using time-hopping spread spectrummultiple access (TH-SSMA), a version of Ultra-Wide Band (UWB), forwireless extension of Asynchronous Transfer Mode (ATM) networks which isdescribed in the article to Win, Moe Z., et. al. entitled “ATM-BasedTH-SSMA Network for Multimedia PCS” published in “IEEE Journal onselected areas in communications”, Vol. 17, No. May 5, 1999. Theirsuggestion is to use TH-SSMA as a wireless “last hop” between a wirelineATM network and mobile devices. Each mobile device would have a uniqueconnection to the closest base station. Each mobile-to-base connectionwould be supplied with a unique time hopping sequence. Transfers wouldhappen asynchronously with each node communicating with the base at anytime using a unique hopping sequence without coordinating with othermobile devices.

[0019] There are significant drawbacks to the TH-SSMA system forsupporting media stream transfers between devices of the network. Thismethod is designed to link an external switched wireline network tomobile nodes, not as a method of implementing a network ofinterconnected wireless nodes. This method relies on the external ATMnetwork to control the virtual path and virtual connections betweendevices. Base stations must be able to handle multiple simultaneousconnections with mobile devices, each with a different time hoppingsequence, adding enormously to the cost and complexity of the basestation. Transfers between mobile devices must travel through the basestation using store and forward. Finally, all mobile nodes areasynchronous, making truly isochronous transfers impossible.

[0020] Accordingly, there is a need for a wireless communication networksystem apparatus which provides for isochronous data transfer betweennode devices of the network, which provides at least one master nodedevice which manages the data transmission between the other nodedevices of the network, and which provides a means for reducing randomerrors induced by multipath fading, and which further providescommunication protocol to provide a means for sharing the transportmedium between the node devices of the network so that each node devicehas a designated transmit time slot for communicating data. The presentinvention satisfies these needs, as well as others, and generallyovercomes the deficiencies found in the background art.

BRIEF DESCRIPTION OF THE INVENTION

[0021] The present invention is a wireless communication network systemfor isochronous data transfer between node devices. In general, thenetwork system comprises a plurality of node devices, wherein each nodedevice is a transceiver. Each transceiver includes a transmitter orother means for transmitting data to the other transceivers as is knownin the art. Each transceiver also includes a receiver or other means forreceiving data from the other transceivers as is known in the art. Oneof the transceivers is preferably structured and configured as a“master” device. Transceivers other than the master device arestructured and configured as “slave” devices. The master device carriesout the operation of managing the data transmission between the nodedevices of the network system. The invention further provides means forframing data transmission and means for synchronizing the network.

[0022] By way of example, and not of limitation, the data transmissionframing means comprises a Medium Access Control protocol which isexecuted on circuitry or other appropriate hardware as is known in theart within each device on the network. The Medium Access Controlprotocol provides a Time Division Multiple Access (TDMA) framedefinition and a framing control function. The TDMA architecture dividesdata transmission time into discrete data “frames”. Frames are furthersubdivided into “slots”. The framing control function carries out theoperation of generating and maintaining the time frame information bydelineating each new frame by Start-Of-Frame (SOF) symbols. These SOFsymbols are used by each of the slave devices on the network toascertain the beginning of each frame from the incoming data stream.

[0023] In the preferred embodiment, the frame definition comprises amaster slot, a command slot, and a plurality of data slots. The masterslot is used for controlling the frame by delineating the SOF symbols.As described in further detail below, the master slot is also used forsynchronizing the network. The command slot is used for sending,requesting and authorizing commands between the master device and theslave devices of the network. The master device uses the command slotfor ascertaining which slave devices are online, offline, or engaged indata transfer. The master device further uses the command slot forauthorizing data transmission requests from each of the slave devices.The slave devices use the command slot for requesting data transmissionand indicating its startup (online) or shutdown (offline) state. Thedata slots are used for data transmission between the node devices ofthe network. Generally, each transmitting device of the network isassigned one or more corresponding data slots within the frame in whichthe device may transmit data directly to another slave device withoutthe need for a “store and forward” scheme as is presently used in theprior art. Preferably, the master dynamically assigns one or more dataslots to slave devices which are requesting to transmit data.Preferably, the data slots are structured and configured to havevariable bit lengths having a granularity of one bit. The presentinvention provides that the master device need not maintaincommunication hardware to provide simultaneous open links between itselfand all the slave devices.

[0024] Broadcast is supported with synchronization assured. Thisguarantees that media can be broadcast to many nodes at the same time.This method allows, for example, synchronized audio data to be sent toseveral speakers at the same time, and allows left and right data to besent in the same frame.

[0025] Asynchronous communication is allowed in certain slots of theframe through the use of either master polling or CSMA-CD afterinvitation from the master.

[0026] The means for synchronizing the network is preferably provided bya clock master function in the master device and a clock recoveryfunction in the slave devices. Each node device in the network systemmaintains a clock running at a multiple of the bit rate of transmission.The clock master function in the master device maintains a “masterclock” for the network. At least once per frame, the clock masterfunction issues a “master sync code” that is typically a unique bitpattern which identifies the sender as the clock master. The clockrecovery function in the slave devices on the network carries out theoperation of recovering clock information from the incoming data streamand synchronizing the slave device to the master device using one ormore correlators which identifies the master sync code and a phase ordelayed locked loop mechanism. In operation, the clock master issues a“master sync code” once per frame in the “master slot”. A slave devicetrying to synchronize with the master clock will scan the incoming datastream for a master sync code using one or more correlators. As eachmaster sync code is received, the phase or delayed locked loop mechanismis used to adjust the phase of the slave clock to that of the incomingdata stream. By providing a common network clock on the master device,with slave devices synchronizing their local clocks to that of themaster clock, support for synchronous and isochronous communication inadditional to asynchronous communication is provided. Time referencebetween all device nodes is highly accurate eliminating most latency andtiming difficulties in isochronous communication links.

[0027] As noted above, each transceiver carries out the operation oftransmitting and receiving data. In wireless transmission, data istransmitted via electromagnetic waves, which are propagated through freespace. In the preferred embodiment, the invention provides datatransmission via baseband wireless technology. This method uses shortRadio Frequency (RF) pulses to spread the power across a large frequencyband and as a consequence reduces the spectral power density and theinterference with any device that uses conventional narrowbandcommunication. This method of transmitting short pulses is also referredto as Ultra Wide Band technology. This present implementation providesbaseband wireless transmission without any carrier. Use of basebandwireless greatly reduces multipath fading and provides a cheaper, easierto integrate solution by eliminating a sinewave carrier. According tothe invention, there is no carrier to add, no carrier to remove, andsignal processing may be done in baseband frequencies.

[0028] Additionally, using short pulses provides another advantage overContinuous Wave (CW) technology in that multipath fading can be avoidedor significantly reduced.

[0029] The present invention further provides a modulator or other meansfor modulating data as is known in the art, a demodulator or other meansfor demodulating data as is known in the art, and a gain controller orother means for controlling the gain of each of the transceivers. In thepreferred embodiment, the means for modulating data comprises amodulator which converts the TDMA frames into streams of basebandpulses. The means for demodulating data comprises a demodulator whichconverts incoming baseband pulses into TDMA frames.

[0030] In a first embodiment, the invention provides pulse modulationand demodulation with on/off keying. The transmitting device modulates a“1” into a pulse. A “0” is indicated as the absence or lack of a pulse.The receiver locks on to the transmitted signal to determine where tosample in the incoming pulse streams. If a pulse appears where thesignal is sampled, a “1” is detected. If no pulse appears, a “0” isdetected.

[0031] In another exemplary embodiment, the invention provides pulsemodulation and demodulation using a pulse amplitude modulation scheme.Here, the transmitting device modulates a digital symbol as a pulseamplitude. For example, a three bit symbol can be represented with eightlevels of pulse amplitude. The receiver locks on to the transmittedsignal to determine where to sample the incoming pulse stream. The levelof the pulse stream is sampled, and the pulse amplitude is converted toa digital symbol.

[0032] The gain controlling means carries out the operation of adjustingthe output gain of the transmitter and adjusting the input gain of thereceiver.

[0033] The network system also includes a hardware interface within theData Link Layer of the Open Systems Interconnection (OSI) ReferenceModel comprising a multiplexer/demultiplexer unit and a plurality ofslot allocation units.

[0034] The master devices described herein, in addition to carrying outits functions as a master device, may also carry out functions as aslave device as described above. For example, the master device may alsoengage in data transfer of non-protocol related data with a slavedevice.

[0035] An object of the invention is to provide a baseband wirelessnetwork system which overcomes the deficiencies in the prior art.

[0036] Another object of the invention is to provide a baseband wirelessnetwork system which provides isochronous data communication between atleast two node devices on the network.

[0037] Another object of the invention is to provide a baseband wirelessnetwork system which provides a master device which manages network datacommunication between the other nodes devices of the network.

[0038] Another object of the invention is to provide a baseband wirelessnetwork system which provides a time division multiple access framedefinition which provides each node device on the network at least onetransmit time slot for data communication.

[0039] Another object of the invention is to provide a baseband wirelessnetwork system which provides a time division multiple access framedefinition which provides means for sharing the data communicationmedium between the node devices on the network.

[0040] Another object of the invention is to provide a baseband wirelessnetwork system which provides baseband wireless data communicationbetween the node devices of the network.

[0041] Further objects and advantages of the invention will be broughtout in the following portions of the specification, wherein the detaileddescription is for the purpose of fully disclosing the preferredembodiment of the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0042] The present invention will be more fully understood by referenceto the following drawings, which are for illustrative purposes only.

[0043]FIG. 1 is a functional block diagram showing a network system inaccordance with the invention.

[0044]FIG. 2 is a functional block diagram of a transceiver node devicein accordance with the invention.

[0045]FIG. 3a is a functional block diagram of a master clocksynchronization unit.

[0046]FIG. 3b is a functional block diagram of a slave clocksynchronization unit.

[0047]FIG. 4 is a time division multiple access frame definition inaccordance with the present invention.

[0048]FIG. 5 is a functional block diagram of the Medium Access Controlhardware interface of the present invention.

[0049]FIG. 6 is a functional block diagram of a slot allocation unitprovided in the Medium Access Control hardware.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Persons of ordinary skill in the art will realize that thefollowing description of the present invention is illustrative only andnot in any way limiting. Other embodiments of the invention will readilysuggest themselves to such skilled persons having the benefit of thisdisclosure.

[0051] Referring more specifically to the drawings, for illustrativepurposes the present invention is embodied in the apparatus shown FIG. 1through FIG. 6. It will be appreciated that the apparatus may vary as toconfiguration and as to details of the parts, and that the method mayvary as to details and the order of the steps, without departing fromthe basic concepts as disclosed herein. The invention is disclosedgenerally in terms of a wireless network for isochronous datacommunication, although numerous other uses for the invention willsuggest themselves to persons of ordinary skill in the art.

[0052] Referring first to FIG. 1, there is shown generally a wirelessnetwork system 10 in accordance with the invention. The network system10 comprises a “master” transceiver device 12 and one or more “slave”transceiver devices 14 a through 14 n. The master device may also bereferred to as a “base” transceiver, and slave devices may also bereferred to as “mobile” transceivers. Master transceiver 12 and slavetransceivers 14 a through 14 n include a transmitter or other means fortransmitting data to the other transceivers of the network 10 via acorresponding antenna 18, 20 a through 20 n. Transceivers 12, 14 athrough 14 n further include a receiver or other means for receivingdata from the other transceivers via its corresponding antenna 18, 20 athrough 20 n. While the illustrative network 10 shows the transceiverdevices 12, 14 a through 14 n using a corresponding single sharedantenna 18, 20 a through 20 n for both transmission and reception,various arrangements known in the art may be used for providing thefunctions carried out by the antenna 18, 20 a through 20 n, includingfor example, providing each of the transceiver devices 12, 14 a through14 n a first antenna for transmission and a second antenna forreception.

[0053] As described further below, the master transceiver 12 carries outthe operation of managing network communication between all transceivers12, 14 a through 14 n of the network 10. The master transceiver 12includes means for managing the data transmission between thetransceiver nodes of the network 10 as described further below.

[0054] Referring now to FIG. 2 as well as FIG. 1, a functional blockdiagram of the “Physical layer” implementation of a transceiver nodedevice 22 in accordance with the present invention is shown. The“Physical layer” as described herein refers to the Physical layeraccording to the Open Systems Interconnection (OSI) Reference Model.This model is based on a proposal developed by the InternationalStandards Organization (ISO) to deal with connecting systems that areopen for communication with other systems.

[0055] Master transceiver 12 and slave transceivers 14 a through 14 n ofthe network 10 are structured and configured as transceiver device 22 asdescribed herein. The transceiver node device 22 comprises an integratedcircuit or like hardware device providing the functions described below.Transceiver device 22 comprises an antenna 24, a transmitter 26connected to the antenna 24, a data modulation unit 28 connected to thetransmitter 26, and an interface to Data Link Layer (DLL) 30 connectedto the data modulation unit 28. The transceiver device 22 also includesa receiver 32 connected to the antenna 24 and a data demodulation unit34 connected to the receiver 32 and to the interface to the interface toData Link Layer (DLL) 30. A receive gain control unit 36 a is connectedto the receiver 32, a transmit gain control unit 36 b is connected tothe transmitter 26. A framing control unit 38 is operatively coupled tothe data modulation unit 28 and the data de-modulation unit 34. A clocksynchronization unit 40 is also operatively coupled to the datamodulation unit 28 and the data demodulation unit 34.

[0056] Antenna 24 comprises a radio-frequency (RF) transducer as isknown in the art and is preferably structured and configured as areceiving antenna and/or a transmitting antenna. As a receiving antenna,antenna 24 converts an electromagnetic (EM) field to an electriccurrent, and as a transmitting antenna, converts an electric current toan EM field. In the preferred embodiment, antenna 24 is structured andconfigured as a ground plane antenna having an edge with a notch orcutout portion operating at a broad spectrum frequency ranging fromabout 2.5 gigahertz (GHz) to about 5 GHz with the center frequency atabout 3.75 GHz. It will be appreciated that antenna 24 may be providedwith various geometric structures in order to accommodate variousfrequency spectrum ranges.

[0057] Transceiver node device 22 includes hardware or circuitry whichprovides an interface to data link layer 30. The interface to data linklayer 30 provides an interface or communication exchange layer betweenthe Physical layer 22 and the “higher” layers according to the OSIreference model. The layer immediately “above” the Physical layer is thedata link layer. Output information which is transmitted from the datalink layer to the interface 30 is communicated to the data modulationunit 28 for further data processing. Conversely, input data from thedata-demodulation unit 34 is communicated to the interface 30, whichthen transfers the data to the data link layer.

[0058] Transceiver node device 22 includes hardware or circuitryproviding data modulation functions shown generally as data modulationunit 28. The data modulation unit 28 carries out the operation ofconverting data received from the interface 30 into an output stream ofpulses. In the case of pulse amplitude modulation, the amplitude of thepulse represents a value for that symbol. The number of bits representedby a pulse depends on the dynamic range and the signal to noise ratio.The simplest case comprises on-off keying, where the presence of a pulseof any amplitude represents a “1”, and the absence of a pulse represents“0”. In this case, data modulation unit 28 causes a pulse to betransmitted at the appropriate bit time to represent a “1” or no pulseto be transmitted at the appropriate time to represents a “0”. Asdescribed further below, the pulse stream produced by transceiver 22must be synchronous with a master clock of the network 10 and must besent at the appropriate time slot according to a frame definitiondefined for the network. The pulse stream is then communicated totransmitter 26 for transmission via antenna 24.

[0059] Transceiver node device 22 includes hardware or circuitryproviding means for transmitting data to other transceivers on thenetwork shown generally as transmitter 26. The transmitting means oftransceiver 22 preferably comprises a wide band transmitter 26.Transmitter 26 is operatively coupled to the data modulation unit 28 andto the antenna 24. Transmitter 26 carries out the operation oftransmitting the pulse stream received from modulation unit 28 andtransmitting the pulse stream as electromagnetic pulses via antenna 24.In the preferred embodiment, information is transmitted via impulseshaving 100 picosecond (ps) risetime and 200 ps width, which correspondsto the 2.5 through 5 GHz bandwidth.

[0060] Transceiver node device 22 includes hardware or circuitry whichprovides means for receiving data from other transceivers showngenerally as receiver 32. The receiving means of transmitter 22preferably comprises a wide band receiver 32. Receiver 32 is operativelycoupled to the antenna 24 and the data demodulation unit 34. Receiver 32carries out the operation of detecting electromagnetic pulse signalsfrom antenna 24 and communicating the pulse stream to the datade-modulation unit 34. The received signal does not necessarily have thesame spectrum content as the transmitted signal, and the spectrumcontent for received and transmitted signals vary according to thereceive and transmit antenna impulse response. Typically, the receivedsignal is shifted toward a lower frequency than the transmitted signal.

[0061] Transceiver node device 22 further includes hardware or circuitryproviding means for controlling the gain of signals received andtransmitted shown generally as gain control units 36 a, 36 b. Thetransmit gain control unit 36 b carries out the operation of controllingthe power output of the transmitter 26 and receive gain control unit 36a carries out the operation of controlling the input gain of thereceiver 32.

[0062] As indicated above, the pulse stream produced by modulator 28must be synchronous with the master clock of the network 10. In order tomaintain a synchronized network, one device must serve the function ofbeing a clock master and maintain the master clock for the network.Preferably, the master device 12 carries out the operation of the clockmaster. All other slave devices must synchronize with the master clock.The invention includes means for synchronizing the network system 10provided by the clock synchronization unit 40 in transceiver 22.

[0063] Referring to FIG. 3a as well as FIG. 1 and FIG. 2, a functionalblock diagram of a clock synchronization unit 40 a for the master device12 is shown. In the master device 12, the clock synchronization unit 40a includes hardware or circuitry providing the functions describedherein. Clock synchronization unit 40 a comprises a clock masterfunction 42 which maintains a master clock 44 for the network 10. Themaster clock 44 runs at a multiple of the bit rate. As described infurther detail below, transmit time is divided into “frames”, andtransceiver devices are assigned specific “slots” within each framewhere the devices are permitted to transmit data. At least once perframe, the clock master function 42 issues a master sync code. Themaster sync code is a unique bit pattern that does not appear anywhereelse in the frame which identifies the sender as the master device 12.

[0064] Referring to FIG. 3b as well as FIG. 1 and FIG. 2, a functionalblock diagram of a clock synchronization unit 40 b for the slave devices14 a through 14 n is shown. In the slave devices 14 a through 14 n, theclock synchronization unit 40 b includes hardware or circuitry providingthe functions described herein. Clock synchronization unit 40 bcomprises a local or slave clock 46 and a clock recovery function 48.The slave clock 46 also runs at a multiple of the bit rate.

[0065] The clock recovery function 48 carries out the operation ofscanning the incoming data stream received by receiver 32 to detect orotherwise ascertain the master sync code using one or more correlators.When the clock recovery function 48 detects the master sync code, theclock recovery function 48 will predict when the next master sync codewill be transmitted. If the new master sync code is detected wherepredicted, the transceiver 22 will be considered “locked” or otherwisesynchronized with the clock master 42 and will continue to monitor andverify future incoming master sync codes. If the clock recovery function48 fails to detect a threshold number of consecutive master sync codes,lock will be considered lost. As each master sync code is received bythe transceiver, a phase or delayed locked loop mechanism is used toadjust the phase of the slave clock 46 to that of the incoming pulsestream.

[0066] The clock recovery function 48 includes a master sync codecorrelator 50. A slave transceiver trying to achieve synchronization or“lock” with the master clock examines the incoming data stream to detectthe master sync code, as described above. The master sync codecorrelator 50 carries out the operation of detecting the first incomingpulse and attempting to match each of the next arriving pulses to thenext predicted or pre-computed pulse. After the initial master sync codeis detected, the clock recovery function 48 of the slave transceiverdevice will perform a coarse phase adjustment of its bit-clock to beclose to that of the incoming pulse stream. When the next master synccode is expected, a mask signal is used to examine the incoming pulsetrain stream only where valid pulses of the incoming master sync codeare expected. The primary edge of the incoming pulse is compared withthe rising edge of the local clock, and any difference in phase isadjusted using a phase-locked loop mechanism. If the incoming pulsestream matches the master sync code searched for, the correlator 50signals a successful match. If the incoming pulse stream differs fromthe master sync code, the process is repeated. Multiple correlators maybe used to perform staggered parallel searches in order to speed up thedetection of the master sync code.

[0067] The clock recovery function 48 further includes a phase lockmechanism 52. As each predicted master sync code is detected at theslave transceivers, the phase lock mechanism 52 carries out theoperation of determining the phase difference between the local slaveclock 46 and the incoming pulses. The phase lock mechanism 52 adjuststhe phase of the slave clock 46 so that the frequency and phase of theslave clock 46 is the same as that of the incoming pulses, therebylocking or synchronizing the local slave clock 46 to master clock 44 ofthe master transceiver 12.

[0068] Referring again to FIG. 2, as well as FIG. 1, the transceivernode device 22 includes hardware or circuitry which providesdemodulating functions and is shown generally as data demodulation unit34. The data demodulation unit 34 carries out the operation ofconverting the input pulse stream from receiver 32 into a data streamfor higher protocol layers. The data de-modulation unit 34 comprises aphase offset detector 54 and a data recovery unit 56. In an isochronousbaseband wireless network, data streams will be received from differenttransceivers with different phase offsets. The phase offset is due topath propagation delays between the transmitter, the receiver and themaster clock 44.

[0069] As described in further detail below, a transmitter will beassigned a data “slot” within a frame to transmit to another device. Thephase offset detector 54 carries out the operation of ascertaining thephase delay between the expected zero-delay pulse location, and theactual position of the incoming pulses. Typically, a known training bitpattern is transmitted before the data is transmitted. The phase offsetdetector 54 in the receiving device detects or otherwise ascertains thetraining bit pattern and determines the phase offset of the incomingpulse from the internal clock. The phase determined is then communicatedto the Data Recovery Unit 56. In the case of pulse amplitude modulation,the training sequence is also used to provide a known pulse amplitudesequence against which the modulated pulse amplitudes can be compared inthe data transmission.

[0070] The Data Recovery Unit 56 in a receiving device carries out theoperation of converting the incoming pulse stream data into bit dataduring time slots that a transmitting device is sending data to thereceiving device. In the case of on-off keying modulation, the datarecovery unit 56 carries out the operation of examining the pulse streamduring the designated time slot or “window” for the presence or absenceof a pulse. In pulse amplitude modulation, the data recovery unit 56carries out the operation of examining the pulse stream during thedesignated time slot or “window” to ascertain the amplitude of the pulsesignal. The “window” or time slot in which the receiving device examinespulse stream data determined by the expected location of the bit due tothe encoding mechanism and the offset determined by the phase offsetdetector 54. The information converted by the data de-modulation unit 34is then communicated to the interface to data link layer 30 for furtherprocessing.

[0071] Referring now to FIG. 4 as well as FIG. 1 and FIG. 2, a TimeDivision Multiple Access (TDMA) frame definition is shown and generallydesignated as 58. The TDMA frame definition 58 is provided and definedby the data link protocol software of the present invention. Moreparticularly, the TDMA frame 58 is defined by the Medium Access Control(MAC) sublayer software residing within the Data Link Layer accordingthe OSI Reference model.

[0072] The means for managing the data transmission between thetransceiver nodes of the network 10 is provided by software algorithmsrunning and executing in the Medium Access Control. The Medium AccessControl protocol provides algorithms, routines and other program meansfor managing and controlling access to the TDMA frame definition 58 andits associated slot components. The architecture of TDMA framedefinition 58 provides for isochronous data communication between thetransceivers 12, 14 a through 14 n of the network 10 by providing ameans for sharing the data transmit time that permits each transceiverof the network to transmit data during a specific time chunk or slot.The TDMA frame architecture divides data transmission time into discretedata “frames”. Frames are further subdivided into “slots”.

[0073] In the preferred embodiment, the TDMA frame definition 58comprises a master slot 60, a command slot 62, and a plurality of dataslots 64 a through 64 n. The master slot 60 contains a synchronizingbeacon or “master sync”. More preferably, the “master sync” is the samecode as the “master sync code” as described earlier for clocksynchronization unit 40. The command slot 62 contains protocol messagesexchanged between the transceiver devices of the network. Generally,each of the data slots 64 a through 64 n provides data transmission timefor a corresponding slave device 14 a through 14 n of the network 10.Preferably, each data slot assigned is structured and configured to havea variable bit width and is dynamically assigned by the master device.In an alternative arrangement, the slave devices 14 a through 14 nrequest the use of one or more of the data slots 64 a through 64 n fordata transmission. In either arrangement, the master may also beassigned one or more slots to transmit data to slave devices. If randomaccess devices are connected to the network, these devices may beassigned a common random access time slot by the master. These deviceswill communicate using a CSMA-CD or similar protocol within theallocated time slot.

[0074] As noted above, the transceiver device 22 includes a framingcontrol function 38. The framing control function 38 carries out theoperation of generating and maintaining the time frame information. Inthe master device 12 the framing control function 38 delineates each newframe by Start-Of-Frame (SOF) symbols. The SOF symbols are uniquesymbols, which do not appear anywhere else within the frame and mark thestart of each frame. In the preferred embodiment, the SOF symbols serveas the “master sync” and as the “master sync code” for the network andare transmitted in the master slot 60 of frame 58. These SOF symbols areused by the framing control function 38 in each of the slave devices 14a through 14 n on the network to ascertain the beginning of each frame58 from the incoming data stream. For example, in one illustrativeembodiment, the invention utilizes a 10-bit SOF “master sync” code of“0111111110”.

[0075] Various encoding schemes known in the art may be used toguarantee that the SOF code will not appear anywhere else in the datasequence of the frame. For example, a common encoding scheme is 4B/5Bencoding, where a 4-bit values is encoded as a 5-bit value. Severalcriteria or “rules” specified in a 4B/5B code table, such as “eachencoded 5-bit value may contain no more than three ones or three zeros”and “each encoded 5-bit value may not end with three ones or threezeros”, ensure that a pulse stream will not have a string of six or moreones or zeros. Other techniques known in the art may also be usedincluding, for example, bit stuffing or zero stuffing.

[0076] The master transceiver 12 carries out the operation of managingnetwork data communication via the exchange of “protocol messages” inthe command slot 62 of frame 58. The master transceiver 12 carries outthe operation of authenticating slave transceivers 14 a through 14 n,assigning and withdrawing data time slots 64 a through 64 n for theslave transceivers 14 a through 14 n, and controlling power of the slavetransceivers 14 a through 14 n.

[0077] Master transceiver 12 authenticates or registers each slavetransceiver by ascertaining the “state” of each of the slavetransceivers of the network 10. Each transceiver operates as afinite-state machine having at least three states: offline, online, andengaged. When a transceiver is in the offline state, the transceiver isconsidered “unregistered” and is not available for communication withthe other devices on the network 10. Each slave transceiver must firstbe “registered” with master transceiver 12 before the slave transceiveris assigned or allocated a data slot within the TDMA frame 58. Once atransceiver is registered with the master transceiver 12, the device isconsidered “online”.

[0078] A slave transceiver that is in the “online” state is ready tosend data or ready to receive data from the other devices on the network10. Additionally, an “online” transceiver is one which is not currentlytransmitting or receiving “non-protocol” data. Non-protocol data is dataother than that used for authenticating the “state” of the transceiverdevices.

[0079] A transceiver is “engaged” when the transceiver is currentlytransmitting and/or receiving “non-protocol” data. Each slave devicemaintains and tracks its state by storing its state informationinternally, usually in random access memory (RAM). The state of eachslave device is further maintained and tracked by the master device 12by storing the states of the slaves in a master table (not shown) storedin RAM.

[0080] In operation, the master transceiver 12 periodically broadcastsan ALOHA packet in the command slot 62 to ascertain or otherwise detect“unregistered” slave devices and to receive command requests from theslave transceivers of then network. More generally, an ALOHA broadcastis an invitation to slave transceivers to send their pending protocolmessages. This arrangement is known as “slotted ALOHA” because allprotocol messages including the ALOHA broadcast are sent during apredetermined time slot. In the preferred embodiment, the ALOHAbroadcast is transmitted at a predetermined interval. Responsive to thisALOHA packet and in the next immediate TDMA frame, an “unregistered”slave device 14 n transmits a signal in command slot 62 identifyingitself as slave device 14 n and acknowledging the master device with aregistration or “discovery” (DISC) request indicating additionalinformation, such as the bandwidth capabilities of the device. When theregistration request is received by the master transceiver 12, themaster table records in the master table that device 14 n is “online”.The master transceiver 12 also transmits a confirmation in command slot62 to the slave device 14 n that the state of slave device 14 n haschanged to “online”.

[0081] When the slave device 14 n receives the confirmation command fromthe master device 12, the slave device 14 n then changes its internalstate to “online”. If more than one slave transceiver replies with anacknowledgement to an ALOHA broadcast in the same frame, a packetcollision may occur because both transceivers are attempting to occupythe same command slot 62 within the frame 58. When a collision isdetected in response to an ALOHA broadcast, the master transceiver 12transmits another ALOHA message directed to a subset of the slavedevices based on a binary-search style scheme, a random delay scheme orother similar searching means known in the art.

[0082] The master transceiver 12 also periodically verifies each slavetransceiver device that is “online” or “engaged” according the mastertable to ascertain whether any failures have occurred at the slavedevice using a “time-out” based scheme. According to this time-outscheme, the master transceiver 12 periodically transmits a POLL packetin command slot 62 to a specific “online” slave device 14 n from themaster table to ascertain the state of the slave device 14 n. In thepreferred embodiment, the master transceiver 12 transmits a POLL signalevery ten seconds. Responsive this POLL packet, slave device 14 ntransmits an acknowledgement signal in the command slot 62 of the nextimmediate frame identifying itself as slave device 14 n andacknowledging its state. Responsive to this acknowledgement signal, themaster transceiver 12 confirms verification of device 14 n and continueswith other tasks. In the event slave device 14 n is shutdown orotherwise unavailable, master transceiver 12 will not receive a returnacknowledgement and master transceiver 12 will fail to verify device 14n. After a predetermined number failed verifications from a slavedevice, a time-out is triggered, and the master transceiver 12 willchange the state of such slave device to “offline”.

[0083] In the command slot 62, the flow of protocol messages between thetransceivers is preferably governed by a “sequence retransmissionrequest” (SRQ) protocol scheme. The SRQ protocol framework providesconfirmation of a protocol transaction after the entire protocolsequence is completed. Effectiveness and success of the transmission ofa protocol sequence are acknowledged at the completion of the entireprotocol sequence rather than immediately after the transmission of eachmessage as in the traditional Automatic Retransmission reQuest (ARQ)approach. Because a protocol sequence may include a plurality ofprotocol messages, the overhead associated with acknowledging eachprotocol message is avoided, and bandwidth use is improved thereby. TheSRQ protocol scheme is described further detail in copending patentapplication entitled “MEDIUM ACCESS CONTROL PROTOCOL FOR CENTRALIZEDWIRELESS NETWORK COMMUNICATION MANAGEMENT” having attorney docket number“INT-99-005” filed on Sep. 10, 1999 which is expressly incorporatedherein by reference.

[0084] Referring again to FIG. 3 as well as FIG. 1 and FIG. 2, aplurality of data slots 64 a through 64 n is provided for each slavetransceiver 14 a through 14 n of the network 10 which is registered as“online”. The master transceiver 12 further manages the transmission ofinformation in slots 64 a through 64 n through traditional Time DivisionMultiple Access (TDMA). The command slot 62 operates in traditional TDMAmode in addition to the “slotted ALOHA” mode described above forinviting protocol messages from the slave transceivers as determined bythe master transceiver 12. The slotted ALOHA mode, which is active whenthe master invites a protocol message, continues until the slaveprotocol message is received without collision. Once the slave protocolmessages is received or “captured” by the master transceiver, thecommand slot operates in a regular TDMA mode until the entire protocolexchange sequence between the master device and the “captured” slavedevice is completed. Traditional TDMA mode is used, for example, when afirst slave transceiver makes a data link request to the mastertransceiver in order to communicate data to a second slave transceiver.

[0085] For example, a first slave transceiver 14 a (microphone) hasaudio data to transmit to a second slave transceiver 14 b (speaker). Themaster transceiver 12 manages this data transaction in the manner andsequence described herein. As indicated above, the master transceiverperiodically sends an ALOHA broadcast to invite protocol messages fromthe slave devices of the network. Responsive to this ALOHA broadcast,slave transceiver 14 a transmits a data-link request (REQ) to mastertransceiver 12 identifying itself as the originating transceiver andidentifying the target slave transceiver 14 b. Responsive to this REQrequest, the master transceiver 12 verifies the states of originating orsource transceiver 14 a and target transceiver 14 a according to themaster table. If both originating transceiver and target transceiver are“online” according to the master table, the master transceiver transmitsa base acknowledge (BACK) to the originating transceiver 14 a and aservice request (SREQ) to the target transceiver indicating the identityof the originating transceiver 14 a and assigns a data slot to theoriginating transceiver 14 a within the TDMA frame 58 for datacommunication. If target transceiver is “offline”, the mastertransceiver 12 transmits a base negative acknowledge (BNACK) packet tothe originating transceiver to confirm the unavailability of the targettransceiver. If the target transceiver is “engaged” in communicationwith another device, the master transceiver 12 transmits a base busy(BBUSY) packet to the originating transceiver to indicate theunavailability of the target transceiver.

[0086] When the originating transceiver 14 a receives the BACK packet,the transceiver 14 a waits for a data-link confirmation from the mastertransceiver 1, after which the transceiver 14 a begins transmitting datawithin a dynamically assigned data slot. Responsive to the SREQ packetfrom the master transceiver 12, the target transceiver 14 b transmits areturn acknowledge (ACK) to the master transceiver 12 indicating thattransceiver 14 b is ready to receive data. The transceiver 14 b alsobegins to monitor the corresponding data slot assigned to theoriginating transceiver 14 a. Responsive to the return ACK from targettransceiver 14 b, the master transceiver 12 transmits a data-linkconfirmation to originating transceiver 14 a to indicate that targettransceiver is ready to receive data communication.

[0087] After originating transceiver 14 a completes its datatransmission to the target transceiver 14 b, the transceiver 14 aterminates its data link by initiating a termination sequence. Asindicated above, the master transceiver 12 will periodically transmit anALOHA broadcast to find unregistered device nodes or to invite protocolrequests from registered device nodes.

[0088] The termination sequence comprises communicating a terminate(TERM) process by the originating transceiver 14 a to the mastertransceiver 12 in response to an ALOHA message from the mastertransceiver 12. In transmitting the TERM message, the originatingtransceiver may also identify the originating device 14 a and the targetdevice 14 b. Responsive to this TERM message, the master transceiver 12carries out the operation of checking the states of the originatingtransceiver 14 a and the target transceiver 14 b, and transmitting totransceiver 14 b a Service Termination (STERM) command.

[0089] The master transceiver verifies the state of the originatingdevice and the target device to confirm that both devices are currentlyengaged for communication. If both devices are engaged, the mastertransceiver 12 transmits a reply BACK message to the originatingtransceiver to acknowledge its termination request and to indicate thatthe status of originating device has been changed to “online” in themaster table. Additionally, master transceiver transmits a STERM messageto target transceiver 14 b to indicate that originating transceiver 14 ais terminating data communication with target transceiver 14 b.

[0090] Responsive to the STERM message, the target transceiver 14 bcarries out the operation of checking its internal state, terminatingthe reception of data, and replying with an acknowledgement (ACK). Thetarget transceiver 14 b first checks its internal state to ensure thatit is engaged in communication with originating transceiver 14 a. Iftarget transceiver 14 b is engaged with a different transceiver, itreplies with a NACK message to the master transceiver 12 to indicatetarget transceiver 14 b is not currently engaged with originatingtransceiver 14 a. If target transceiver 14 b is engaged with transceiver14 a, then target transceiver 14 b stops receiving data from transceiver14 a and sets its internal state to “online”. Target transceiver 14 bthen transmits to master transceiver 12 an ACK message to indicate thatit has terminated communication with transceiver 14 a and that it haschanged it state to “online”.

[0091] When the master transceiver 12 receives the ACK message from thetarget transceiver 14 b, it changes the state of target transceiver 14 bin the master table to “online” and replies to target transceiver 14 bwith a confirmation of the state change. The master transceiver 12 alsoconsiders the data slot which was assigned to originating transceiver 14a as released from use and available for reallocation. When a NACKmessage is received by master transceiver 12 from target transceiver 14b, a severe error is recognized by master transceiver 12 because thisstate was not previously registered with the master table. The mastertransceiver then attempts a STERM sequence with the remaining relatedslave devices until the proper target transceiver is discovered orotherwise ascertained.

[0092] When a user of a slave device terminates or interrupts power tothe slave or otherwise makes the slave unavailable for communication,the device preferably initiates a shutdown sequence prior to suchtermination. The shutdown sequence comprises a shutdown (SHUT) messagefrom the slave device 14 n to the master transceiver 12, in response toan ALOHA broadcast from the master 12. Responsive to the SHUT message,the master 12 replies to the slave device 14 n with a BACK messageindicating that state of slave device 14 n has been changed to “offline”in the master table. Responsive to the BACK message, the slave device 14n changes its internal state to “offline” and shuts down.

[0093] Referring now to FIG. 5, a functional block diagram of the MediumAccess Control hardware interface of the present invention is shown andgenerally designated as MAC 66. In general, the MAC 66 is provided atthe Data Link Layer between the Network Layer and the Physical Layer ofthe OSI reference model. More particularly, the MAC 66 provides thehardware circuitry within Medium Access Control (MAC) sublayer of theData Link Layer according the OSI reference model. The Medium AccessControl protocol provided by the present invention provides the softwarefor controlling the processes of the various components of the MAC 66 asdescribed below.

[0094] The MAC 66 comprises an integrated circuit or like hardwaredevice providing the functions described herein. The MAC 66 providesmeans associated with each transceiver for connecting multiple datalinks received from the Logical Link Layer to a single physical TDMAlink. The MAC 66 comprises a communication interface 68 for providingcommunication with the Medium Access Control Protocol 69, a PhysicalLayer interface 70 for communication with the Physical layer, aplurality of slot allocation units (SAU) 72 a through 72 n eachoperatively coupled to the communication interface 68, aMultiplexer/Demultiplexer (Mux/Demux) unit 74 operatively coupled to thePhysical Layer interface 70 and each of the SAU 72 a through 72 n, and aLogical Link Control (LLC) interface 73 connected to each of the SAU 72a through 72 n. A plurality of data interfaces 76 a through 76 n arealso provided for transmitting data to and receiving data from the LLCinterface 73. Each data interface 76 a through 76 n is connected to acorresponding SAU 72 a through 72 n.

[0095] Data streams in the present invention will flow in bothdirections. For example, output data will be transmitted from higherlevel protocols through the DLL hardware 66 and out to the PhysicalLayer via interface 70. Input data is received from the Physical Layerthrough interface 70 into the MAC 66 and then communicated to the higherlevel protocols. Within the MAC 66 the data path comprises the datainterfaces 76 a through 76 n connected to the SAU 72 a through 2 n, theSAU 72 a through 72 n connected to the Mux/Demux 74, and the Mux/Demux74 connected to the Physical Layer interface 70. The direction of dataflow within each SAU 72 a through 72 n is controlled by the MediumAccess Control protocol 69 via communication interface 68. Thecommunication interface 68 is preferably separated from the data paththrough MAC 66. This arrangement provides simple data sources, such asaudio streaming devices, a direct connection to the MAC 66.

[0096] The Mux/Demux 74 carries out the operation of merging outgoingdata streams from the SAU 72 a through 72 n into a single signaltransmitted by the Physical Layer. In the preferred embodiment, a TDMAscheme is used for data transmission. Under the TDMA multiple accessdefinition scheme, only one device may be transmitting at any giventime. In this case, the Mux/Demux 74 is connected to the outputs of eachSAU. The output of the Mux/Demux 74 is then operatively coupled to thePhysical Layer interface 70. The Mux/Demux 74 also carries out theoperation of distributing incoming network data received from thePhysical Layer via interface 70 into the SAU 72 a through 72 n.Generally, the currently active SAU will receive this incoming data.

[0097] Referring now to FIG. 6 as well as FIG. 5, a block diagram of anSAU unit is shown and designated as 72. Each SAU unit 72 a through 72 nare structured and configured as SAU 72. SAU 72 comprises an outputbuffer unit 78, an input buffer unit 80, a control logic unit 82connected to the output buffer unit 78 and the input buffer unit 80, andcontrol status registers 84 connected to the control logic unit 82. Theoutput buffer unit 78 stores data to be transmitted from a first deviceto another device in a First-In-First-Out (FIFO) buffer (not shown),encodes the buffer's output using a 4B/5B or similar encoding scheme andprovides the resulting bit stream to the Mux/Demux unit 74 via line 86a. The data to be transmitted is provided through the interface 73 vialine 85 a. The input buffer unit 80 receives data from the Physicallayer through the Mux/Demux unit 74 via line 86 b, decodes it accordingthe same 4B/5B or similar encoding scheme, and stores the data in a FIFObuffer (not shown) which is connected to the data path interface 73 vialine 85 b. Lines 85 a and 85 b are operatively coupled to datainterfaces 76 a through 76 n for communication with interface 73. Lines86 a and 86 b are operatively coupled for communication with Mux/Demuxunit 74.

[0098] The control logic unit 82 comprises a state machine that controlsthe operation of the output buffer unit 78 and input buffer unit 80 aswell as the communication between the MAC and the Logical Link Layer(LLC), and the MAC and the Physical Layer. The values of the controlregisters 84 are set by the LLC above the MAC layer via line 88 andcontrol the operation of the SAU.

[0099] The control registers 84 comprise a SAU enable register 90, adata transfer direction register 92, a slot start time register 94, anda slot length register 96. The SAU enable register 90 determines whetherthe SAU 72 should transmit or receive data. The data transfer directionregister 92 determines whether the SAU 72 is set up to transmit to thePhysical Layer or to receive from the Physical Layer. The slot starttime register 94 provides the SAU 72 with the time offset of the slotmeasured from the start of the frame, during which the SAU 72 transmitsdata to the Physical Layer.

[0100] The slot length register 96 determines the length of the slot.The status registers 84 provide the LLC with information about thecurrent state of the SAU. The status registers comprise an input bufferunit empty flag, an input buffer unit full flag, an output buffer unitempty flag, an output buffer unit full flag, and an input decoder errorcounter. The buffer unit empty flag indicate whether the respectivebuffer units are empty (i.e., contain no data). The buffer unit fullflag indicate whether the respective buffer units are full (i.e., cannotstore additional data). The input decoder error counter indicates thenumber of error detected during the decoding of data arriving from thePhysical Layer.

[0101] The SAU 72 transmits or receives data autonomously after beingset up by the LLC. The setup consists of writing appropriate values intothe data transfer direction register 92, the slot start time register94, and the slot length register 96 and then enabling the SAU 72 byasserting the SAU enable register 90. The slot start time and slotlength values provided in registers 94, 96 respectively are designatedto the communicating device by the network master 12. These values aredetermined by the master 12 in such a way that no two transmitters inthe network transmit at the same time, a requirement of the TDMAcommunication scheme. During transmission, the SAU 72 will monitor thecurrent time offset within the frame and compare it with the slot starttime. When the two values are equal, the SAU 72 will provide thePhysical Layer with encoded data bits from the output buffer 78 untilthe frame has reached the end of the time slot allocated to the SAU 72as determined by the slot length register 96. If the output FIFO bufferis empty during the allocated time slot, the SAU 72 will transmitspecial bit codes indicating to the receiver that there is no data beingtransmitted.

[0102] Likewise, the SAU 72 will monitor the current time offset withinthe frame during data reception and compare it to the slot start timeregister 94. When the two values are equal, the SAU 72 will acquire datafrom the Physical Layer through the Mux/Demux Unit 74, decode it andstore the decoded data in the input FIFO buffer. If the decoder detectsa transmission error, such as a bit code sequence not found in the 4B/5Bencoding table, the data stored in the input FIFO buffer is marked asinvalid and the input decoder error counter is incremented. If thedecoder detects special bit codes indicating empty data, the latter areignored and will not be stored in the input FIFO buffer.

[0103] Accordingly, it will be seen that this invention provides awireless communication network system for isochronous data transferbetween node devices of the network, which provides a master node devicehaving means for managing the data transmission between the other nodedevices of the network system, which further provides means for framingdata transmission and means for synchronizing the network communicationprotocol, thus providing a means for sharing the transport mediumbetween the node devices of the network so that each node device has adesignated transmit time slot for communicating data. Although thedescription above contains many specificities, these should not beconstrued as limiting the scope of the invention but as merely providingan illustration of the presently preferred embodiment of the invention.Thus the scope of this invention should be determined by the appendedclaims and their legal equivalents.

What is claimed is:
 1. A wireless communication network systemcomprising at least three transceivers, each said transceiver having atransmitter and a receiver, one of said transceivers being structuredand configured as a master device, said master device structured andconfigured to manage data transmission between said transceivers.
 2. Thewireless communication network system as recited in claim 1, whereinsaid transceivers operate according to a Medium Access Control protocolhaving a time division multiple access frame definition, said protocolstructured and configured to operate in aloha mode and time divisionmultiple access mode.
 3. The wireless communication network system asrecited in claim 1, wherein each said transceiver further comprises aframing controller, said framing controller having means for generatingand maintaining time frame information for said network system.
 4. Thewireless communication network system as recited in claim 1, furthercomprising a frame definition having a master slot, a command slot, anda plurality of data slots, said master slot having a master sync code,said protocol operating in slotted aloha mode and time division multipleaccess mode, said master device managing said protocol and said dataslots in said protocol.
 5. The wireless communication network system asrecited in claim 1, further comprising a Medium Access Control hardwareinterface comprising a multiplexer/demultiplexer unit and a plurality ofslot allocation units, said multiplexer/demultiplexer unit operativelycoupled to said plurality of slot allocation units.
 6. The wirelesscommunication network system as recited in claim 1, wherein saidtransmitters are structured and configured to emit radio frequencypulses operating with baseband wireless technology and said receiversare structured and configured to receive radio frequency pulses.
 7. Thewireless communication network system as recited in claim 1, whereinsaid transmitters are structured and configured to emit radio frequencypulses operating with ultra-wide band wireless technology and saidreceivers are structured and configured to receive radio frequencypulses.
 8. The wireless communication network system as recited in claim1, wherein said transceivers are structured and configured to transferdata to other said transceivers isochronously.
 9. The wirelesscommunication network system as recited in claim 1, wherein each saidslave transceiver further comprises a local clock therein, said mastertransceiver further comprising a master clock therein, each said localclock synchronized with said master clock
 10. A wireless communicationnetwork system comprising: (a) at least three transceivers, one of whichis structured and configured as a master device to manage datatransmission between said transceivers; (b) a transmitter in each saidtransceiver; and (c) a receiver in each said transceiver.
 11. Thewireless communication network system as recited in claim 10, whereinsaid master device includes a time division multiple access framedefinition and a framing control function to frame data transmissionbetween said transceivers.
 12. The wireless communication network systemas recited in claim 10, wherein said transceivers operate according to atime division multiple access frame definition to synchronize saidnetwork system.
 13. The wireless communication network system as recitedin claim 10, wherein each said transceiver further comprises: (a) a datamodulator; and (b) a data demodulator.
 14. The wireless communicationnetwork system as recited in claim 10, further comprising a timedivision multiple access frame structure having a master slot, a commandslot, and a plurality of data slots.
 15. The wireless communicationnetwork system as recited in claim 10, further comprising a MediumAccess Control unit comprising a Physical layer interface, amultiplexer/demultiplexer unit operatively coupled to said Physicallayer interface, a plurality of slot allocation units operativelycoupled to said multiplexer/demultiplexer unit, an interface to higherlevel protocols operatively coupled to said plurality of slot allocationunits.
 16. A method for providing wireless network communicationcomprising the steps of: (a) providing a master transceiver; (b)providing a plurality of slave transceivers in communication with saidmaster transceiver; (c) synchronizing said slave transceivers with saidmaster transceiver; (d) providing a Medium Access Control protocol whichis executed in said master transceiver and in said slave transceivers,said protocol including a Time Division Multiple Access frame definitionhaving a master slot, a command slot, a plurality of variable lengthdata slots; (e) requesting a data slot from said master transceiver by asource slave transceiver; (f) assigning to said source slave transceiveran assigned data slot by said master transceiver; and (g) after saidassigning step, transferring data in said assigned data slot, by saidsource slave transceiver, to a target slave transceiver, said datatransferring carried out without intervention from said mastertransceiver.